1. Technical Field
The present invention relates in general to a multiplexing system and method and in particular to a multiplexing system and method for servicing RAID devices. Still more particularly, the present invention relates to a multiplexing system and method that provides a single service link for multiple targets or disk drives within a RAID system, which allows easy access or remote access to an individual drive within the RAID system.
2. Description of the Related Art
RAID systems have an array of disk drives linked together. A RAID controller makes the array of disk drives within a RAID system look like one large and reliable disk. A typical RAID system has the disk drives serially linked together. FIG. 1 shows a prior art serial storage architecture (SSA) configuration 10 wherein the disk drives (DASD) 14, 20, 26, to N are serially linked together and linked to a SSA initiator 12. The SSA 10 is coupled to a controller card 36 via a device service interface (DSI) 32, that is, each of the disk drives (DASD) 14, 20, 26, to N are coupled to the controller card 36 via the DSI 32. A display 34, a serial node bypass card (SNBC) 38, and a power sequencer (PWR SQNR) 40 are coupled to the controller card 36. The controller card 36 also has a service link 37 that couples to a service unit interface 42. The SNBC 38 and the PWR SQNR 40 may also each have a service link that couples to a service unit interface 42. The service unit interface 42 of a disk drive, the controller card 36, the SNBC 38, or the PWR SQNR 40 receives and couples a service unit, such as the IBM RS232 service unit, to the respective device or sub-system.
When a drastic problem with a RAID disk drive occurs, data in the disk drive is not accessible. The disk drive is accessed by communicating with the controller card 36 and the DSI 32 at the back plane of the drawer of the disk drive. However, the DSI 32 is typically not functional when a drastic problem occurs, and the disk drive is unable to be accessed via the DSI 32. Points of failure at the controller card 36 and the DSI 32 prohibits access and communications to the respective disk drive.
The disk drive and the data therein would have to be accessed through a service unit interface 42, that is, coupling a RS232 service unit to the interface 42 of the disk drive to be serviced and to the interface 42 of the controller card 37. However, the disk drives 14, 20, 26, to N are located in drawers. One problem with these drawers is that the disk drive powers down when the drive latch is open. If the disk drive is powered down or is moved to another location for servicing, volatile data may be lost. Data written on the disk drive would most likely still exist, but data such as error registers would be lost. Therefore, due to the physical carrier of the disk drives, the service unit interface 42 is not able to be or not easily accessible by a service technician or other such personnel. Cumbersome and inconvenient solutions, such as cutting the front of the drive unit or drawer and using temporary connections from the service unit (RS232 unit) to the service unit interface 42, have been implemented to maintain the power of the disk drive while still being able to access the service unit interface 42.
It would therefore be advantageous and desirable to have a multiplexing system and method for servicing serially linked targets or RAID devices. It would be advantageous and desirable to have a multiplexing system and method that provides a single service link for multiple targets, which allows easy access or remote access to an individual target. It would be advantageous and desirable to have a multiplexing system and method that provides a single service link for multiple disk drives within a RAID system, which allows easy access or remote access to an individual drive within the RAID system. It would also be advantageous and desirable to provide a system and method that does not require physical alterations or powering down or moving of the target or disk drive that needs to be serviced.
It is therefore one object of the present invention to provide a multiplexing system and method for servicing targets or serially linked devices.
It is another object of the present invention to provide a multiplexing system and method for servicing RAID devices.
It is still another object of the present invention to provide a multiplexing system and method that provides a single service link for multiple targets or serially linked devices, which allows easy access or remote access to an individual target.
It is still another object of the present invention to provide a multiplexing system and method that provides a single service link for multiple disk drives within a RAID system, which allows easy access or remote access to an individual drive within the RAID system.
It is yet another object of the present invention to provide a system and method that does not require physical alterations or powering down or moving of the disk drive that needs to be serviced.
It is still yet another object of the present invention to provide a system and method that allows direct or remote access and communications with a target or drive within a number of serially linked targets or drives.
It is still another object of the present invention to allow service links from other computer devices to be linked to a common multiplexing or switching system.
The foregoing objects are achieved as is now described. A multiplexing system and method for servicing serially linked targets or RAID devices. The multiplexing system couples service interfaces from various targets and devices. The multiplexing system provides a single service link to a single service unit interface. The single service link allows easy access/communications or remote access/communications to an individual target or disk drive within the RAID system. A service unit is directly or remotely coupled to the service unit interface. The multiplexing system has an outgoing multiplexer, an in-going multiplexer, and a multiplexer controller. The service unit communicates with the multiplexing system to select the desired target or disk drive to be serviced. The multiplexer controller detects incoming select target commands and compares incoming target address information with a presently defined multiplexer controller target address information. A switch command is activated or occurs when the incoming select target address information is different with the presently defined multiplexer controller target address information. The multiplexing system accordingly switches to a different target or disk drive to be looked at and serviced when a switch command has been activated or has occurred.
The above as well as additional objects, features, and advantages of the present invention will become apparent in the following detailed written description.